Digital Signal Processing Reference
In-Depth Information
laws tell us that they will have equal voltages at the connection and equal currents
flowing through them. Thus, our Bergeron diagram gives us the solution to two
simultaneous Ohm's law equations in two unknowns (the voltage and current)
via graphical means.
By continuing to draw load lines for the transmission lines with slopes that
alternate between
1
/Z
0
we can find the voltage and current levels at each end
of the line as the waves propagate back and forth. For example, Figure 11-20c
shows the extension of the next transmission load line back to the transmitter
load line, which gives the signal levels at the transmitter after a round-trip
propagation delay. The transient wave components are becoming small enough
±
Tx Pull-Down
200
0)
(0.357 V, 28.6 mA)
Tx (
t
<
100
R
x
0
T-line
0)
(2.357 V,
−
11.4 mA)
Tx (
t
=
−
100
−
200
Tx Pull-Up
300
−
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Voltage [V]
(a)
Tx Pull-Down
200
0)
(0.357 V, 28.6 mA)
Tx (
t
<
100
R
x
0
T-line
Tx (
t
=
0)
t
d
)
(2.757 V,
−
3.4 mA)
Rx (
t
=
−
100
(2.357 V,
−
11.4 mA)
−
200
Tx Pull-Up
−
300
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Voltage [V]
(b)
Figure 11-20
Bergeron diagram construction sequence for Example 11-3: (a) initial
wave at transmitter (
t
=
0); (b) receiver (
t
=
t
d
); (c) transmitter (
t
=
2
t
d
); (d) close-up:
transmitter (
t
=
2
t
d
).
(Continued)
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